In a setting device disclosed in an advertisement sheet entitled 1.5.8.1 "Telegramm" issued by the applicant in 1983, a feeler assembly is mounted on a plate which is in turn mounted for axial displacement in a housing. The feeler assembly is engaged to the plate and housing by a threaded spindle operable to adjust the axial position of the feeler assembly relative to a retainer shaft and to a switching sleeve to thereby set a switch-off point to the desired screw-tightening depth. The retainer shaft is axially displaceable within the housing. The switching sleeve is axially displaceable relative to the retainer shaft while being movable in unison therewith over a predetermined axial range. The adjustment of the switch-off point by altering the axial position of the feeler assembly is in practice encumbered by difficulty in finding its desired axial position. The adjustment of the switch-off point is thus rather time consuming and troublesome in this known device. Also, the construction of the components for the adjustment of the feeler assembly is rather complicated. In addition, the adjustment assembly comprises outward projecting parts at variance with the desire to provide a compact device having a smooth exterior.
In a screw-driving device of a different type described in U.S. Pat. No. 2,446,363 the biasing nut of a friction clutch threaded on a hollow drive shaft within the housing is adjusted by means of a turning tool engaging the biasing nut through outward opening slots in the housing. The adjustment of the biasing nut merely alters the limit torque of the friction clutch, so that this known device does not in any manner suggest the general principle for an adjustment of the switch-off point.
U.S. Pat. No. 2,989,996 also discloses a screw-driving device of a different type. For retracting the screw-driving tool within the housing a control flange is mounted for displacement in unison with the screw-driving tool. When the preset screw-tightening depth is reached, the control flange cooperates with a crank lever pivotally mounted on the exterior of the housing to actuate a valve for a retraction mechanism. The screw-tightening depth is adjusted by means of an adjustment assembly, again mounted to the exterior of the housing.